710 REPOET— 1886. 



are very similar to tlie European, whilst the marine species of these groups differ- 

 very much in the two localities. He concludes that these freshwater fonns are very 

 old and conservative, and may be supposed to be the unchanged offspring of old 

 ancestral forms, as such possessing particular systematic importance. 



3. On a Sponge possessing Tetragonal Symmetry, ivith Observations on the 

 Minute Structure of the Tetractinellidoe. By Professor Sollas, LL.D. 



4. The Anatomy of Neaera. By Professor Haddon. 



5. The Nervous System of Sponges. By Dr. R. Von Lendenfeld. 



The aiithor gives an account of his discoveries on this subject up to date. 

 Sensitive and ganglia cells have been observed by him in a number of sponges.. 

 Their locality varies, their shape is constant. They are mesodermal, and appear to 

 preside over the movements of the membranes and pore-sieves, and so regulate the 

 water-ciuTent. The great difference between sponges and higher ccelenterates is,. 

 that in the former the most important organs are mesodermal, whilst in the latter 

 they are ecto- or ento-dermal. He divides the type Ocelenterata accordingly into 

 Ccelenterata mesodermalia, or sponges, and Ccelenterata epithelaria or Cnidaria, as- 

 sub- types. 



6. The Function of Nettle-cells. By Dr. R. Von Lendenfeld. 



The author gives a detailed account of the structure of the nettle-cells, or 

 cnidoblasts, and discusses some biological facts regarding their function. He 

 comes to the conclusion that the nettle-cells are exploded by direct reflex action 

 when the cnidocil is touched ; but that the animal can counteract this reflex action. 

 by a centrifugally acting nervous irritation, in the same w-ay as reflex actions are 

 controlled by higher nervous centres in man. 



7. Note on a peculiar Medusa from St. A^idrev/s Bay. 

 By Professor McIntosh, If.D., LL.D., F.E.S. 



When using the large net (with the fine mesh) attached to the triangle of wood,, 

 as described in the Eeport of the Marine Laboratory, presented to the Association, 

 one of the earliest sweeps (August 9), north of the' pier at the depth of 3 fathoms,, 

 in 5 fathoms' water, brought iu a Medusa hitherto unknown to me. It occurred 

 amidst swarms of Thaumantias, Bougainvillea, Oceania, Turris, Cyanea, Aurelia, 

 Plewobrachia and Beroe, but was readily distinguished by the presence of a simple 

 pale cross on the translucent hyaline disc. The same form was again met with 

 about a fortnight later off the East Rocks. 



It is of considerable size, its disc measuring about five inches in diameter. It 

 has the ordinary shape, viz., moderately convex dorsally, somewhat flattened 

 venti-ally, and presents no novelty in the microscopic structure of its hyaline tissue. 

 The margin is surrounded by a closely arranged series of tentacles of considerable 

 length. These taper from base to apex, each moreover having a single small black 

 pigment-speck at the base. The latter shows no special differentiation, only a 

 group of simple pigment-granules. Within the bases of the tentacles is a narrow 

 trilled membrane, apparently the velum, and this is especially distinct during the 

 contractions of the disc. 



The reproductive bands begin a short distance within the margin, and extend 

 along the representatives of the radiating tubes right across the disc in each case, 

 thus forming a conspicuous cross. These bands are somewhat regularly folded 

 or lobulated at the margin, and have a pale grey or dull whitish colour. The 

 elements do not seem to be much developed, the minute cells which distend the 

 i'rills being finely granular. 



